This invention relates to magnetic refrigeration and more particularly to refrigeration between about 12 to about 77K with an apparatus utilizing a belt carrying ferro or paramagnetic material having Curie temperatures between 15K and 85K. This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).
Magnetic refrigerators such as disclosed in U.S. Pat. No. 4,332,135 issued to Barclay et al. and U.S. Pat. No. 4,408,463 issued to Barclay are known and the two patents are specifically incorporated herein by reference. Such magnetic refrigerators utilized paramagnetic or ferromagnetic material and moved the material in and out of the magnetic field, causing the material to magnetize and demagnetize. U.S. Pat. No. 4,408,463 showed ferro or paramagnetic porous material disposed within a wheel with the material nearest the inside rim having a lower Curie temperature than the material near the outer rim. One section of the circumference of the wheel was disposed within a solenoid-shaped magnet. The geometry of this arrangement limited the thickness of the wheel rim that could pass through the open bore of the solenoidal-shaped magnet. Additionally, this arrangement allowed only one refrigeration cycle per revolution of the wheel. Assembly of the refrigerator was also difficult because of the need for a split wheel and a split housing around the wheel.
There was, however, still a need for an efficient arrangement of magnet and magnetic material which would allow more magnetic material to be exposed to the magnetic field for a given size of magnet. In addition, a need existed for a magnetic refrigerator design that had an easily assembled housing surrounding the magnetic material travel path and was at the same time compact. The instant invention utilizes a belt configuration of magnetic material which can more completely fill the bore of a solenoidal-shaped magnet, and yet not require a split belt or a split housing. Additionally, the belt can allow two passes through the magnetic field for each complete circuit of the loop path that the belt is shaped into.